While each day brings new understanding of the importance of sufficient amounts of quality sleep, the western world’s concept of a continuous eight hours or more is pretty much a modern invention. When we look back in time before the 1800’s and the industrial revolution, the common way to sleep was in two different sessions with a pretty long break of being awake in between.
Today, it seems strange to the majority of us that people of the ancient world had sleeping patterns that were broken up into dual four-hour segments, with the first beginning about two hours after nightfall. Cultural anthropologists and others within the sciences community refer to this as biphasic, or bi-modal.
This was not only the normal way to sleep in westernized countries such as Europe and the U.S., but was the norm for the entire world. In fact, the norm around the world in non-westernized countries historically and in the present day is polyphasic sleep, where sleep may be broken up into two or more sessions throughout the 24-hour period.
It was Virginia Tech History Professor Roger Ekirch that is credited with being the first to track the evolution of our ancient sleep patterns in the U.S. To be fair though, there have been quite a few leaders across the sciences studying human history and biology that have studied and contributed to the world’s patterns of sleep.
Here in the U.S., people living in the 18th century slept in two shorter periods over a 12-hour range. The first session lasted about four hours followed by wakefulness of several hours, which was followed by sleep until morning.
That time spent awake was used for study, contemplation, visiting neighbors or conceiving children. Many theorize that it grew out of the hunter gatherer period where we had to wake to tend the fire during the night. Researchers have found that this period of wakefulness was a period of great calm for people, which was similar to meditation in many instances.
The advent of street lights and indoor lighting is often credited for the wholesale change to a single eight-hour sleep pattern in the U.S. Today, we panic if we wake up during the night unexpectedly, which measurably raises our stress levels.
A number of researchers across disciplines have surmised that it could be a biological imperative that fostered our biphasic sleep patterns. To test this theory, psychiatrist Thomas Wehr of National Institutes of Mental Health conducted a study in the early ‘90s on photoperiodicity (exposure to light), and its effect on sleep patterns.
The study had fifteen men stay up for 10 rather than the normal sixteen hours with the light restricted for the remaining hours of the 24-hour period. For fourteen hours a day for four weeks, they were in a closed darkened room and encouraged to rest and sleep as much as possible. After an initial period where the participants caught up on lost sleep accumulated before the study, they began to sleep in a bimodal pattern like people of the past and the rest of the world.
While this type of sleep pattern is attainable in the U.S. where a significant number of people have adopted it, the jury is still out on whether this potentially biological imperative leaves us more rested. The study of Circadian Rhythms and how they influence our health and sleep patterns is always a consideration and part of any scientific study of humans and sleep.
When we look at the non-westernized countries of the world today, we are in the minority as, by and large, the world sleeps polyphasic. What is important to note is that despite some of the noisiest environments in the world and an ancient habit of sleeping in groups that persist today, they still get the same eight hours or more of sleep.
In spite of gaining an understanding that “normal” sleep patterns are both subjective and culturally dependent, the quality of the sleep is still a major factor in terms of our bodies and health. Stresses of the modern world and chronic sleep problems such as sleep apnea are very real biological challenges that make it impossible for people to get the restful sleep their bodies need without some support. What is clear is that everything that we learn about our past and our present when it comes to sleep can be utilized collectively to enhance our quality of life and health in myriad ways.